1. Field of the Invention
This invention relates to a self-aligning roller bearing with retainer which can be installed in various kinds of mechanical devices, for example, to support a rotating shaft inside a housing.
2. Description of the Related Art
Conventionally, in order to freely rotatably support a heavy shaft inside a housing, a self-aligning roller bearing with retainer as shown in JP Patent First Publication KOKAI No. H5-157116 was used. As in FIG. 1, this kind of self-aligning roller bearing with retainer comprises an outer ring 1, an inner ring 2 arranged concentric with the outer ring 1, a plurality of convex rollers 3 located in two rows between the outer ring 1 and the inner ring 2 and arranged so that they turn freely, and a pair of retainers or cages 4 used for preventing the convex rollers 3 from becoming separated. The retainers or cages 4 are made by press-forming a metal plate and referred to as press retainers or cages.
An outer raceway 5 having a spherical concave surface with a single center is formed on the inner peripheral surface of the outer ring 1. Also, a pair of inner raceways 6 are formed on the outer peripheral surface of the inner ring 2 and juxtaposed in the axial direction of the roller bearing (left and right direction of FIG. 1) to face the outer raceway 5. The convex rollers 3 are respectively formed generally symmetrically in the direction of roller axis with the section having the largest diameter located in the axial center of the roller length in the direction of roller axis, and arranged in two rows between the outer raceway 5 and the pair of inner raceways 6 so that they turn freely. It will be noted that the roller axis is tilted by a predetermined amount with reference to the axial direction of the roller bearing.
The retainers or cages 4 as shown in FIGS. 1 and 2 has a main part 7 having larger and smaller diameter sections in a frustum shape, an outward flange 8 extending outward in the radial direction from the peripheral edge of the larger diameter section of the main part 7, and an inward flange 9 extending inward in the radial direction from the peripheral edge of the smaller diameter section of the main part 7.
There are a plurality of pockets 10 formed in the main part 7, wherein each of the pockets 10 supports one of the convex rollers 3 so that it turns freely.
In addition, the roller bearing has a guide ring 11 which is freely rotatably located between the two rows of convex rollers 3.
The outward flanges 8 of the pair of retainers 4 are guided by the guide ring 11 with the outer peripheral edge of the outward flanges 8 fitted into the inner peripheral surface of the guide ring 11.
The guide ring 11 has the either axial side thereof positioned closer to the axially inside end face of the convex rollers 3 to guide the convex rollers 3 so that the rotational axis or roller axis of the convex rollers 3 is prevented from being inclined or "skewed" from its normal condition.
The term "axially inside" in the present specification means the central portion side of the roller bearing while the term "axially outside" means the open end side of the roller bearing.
In the self-aligning roller bearing with retainer described above, in order that a rotating shaft (not shown) is supported inside the housing (not shown), the outer ring 1 is inserted into and fixed to the housing with the inner ring 2 fixed from outside to the rotating shaft. When the inner ring 2 rotates together with the rotating shaft, the convex rollers 3 turn allowing the rotating shaft to rotate. If the axis of the housing does not coincide with the axis of the rotating shaft, the inner ring 2 is aligned inside the outer ring 1 to compensate for the non-coincidence. Specifically the central axis of the inner ring 2 is inclined with respect to the central axis of the outer ring 1. Because the outer race 5 is formed with a single spherical surface, rotation of the convex rollers 3 is smooth even after compensation of the non-coincidence.
Used in the self-aligning roller bearing with retainer in FIG. 3 are the retainers 4 which do not have the outwardly extending flanges 8 of FIGS. 1 and 2, and instead are formed such that the inner peripheral face of the axially inside end portion of the retainers 4 is positioned close to the outer peripheral edge of the guide ring 11.
In the case of FIG. 3, the guide ring 11 has its either side face positioned closer to the axially inside end face of the convex rollers 3 for guide so as to prevent the convex rollers 3 from skewing.
There are problems in the prior art self-aligning roller bearings with retainer as follows.
Specifically, when a larger load is applied in an axial direction (left-right direction in FIGS. 1 and 3) in the self-aligning roller bearing with retainer, one row of the convex rollers 3 has its rolling surface strongly abutted to the outer raceway 5 and the inner raceway 6 to support the load while the other row of the rollers 3 does not.
There is substantially no contact pressure between the rolling face of the convex rollers 3 in the other row and the outer and inner ring raceways 5 and 6, so that the other row of the convex rollers 3 can be moved in the axial direction of the roller bearing. Accordingly, the guide rings 11 can be displaced toward the other row of the convex rollers 3, increasing the distance between the axially inside end face of the convex rollers 3 in the one row and the corresponding side face of the guide ring 11. In this case, the rollers 3 in the one row is readily skewed.
When the self-aligning roller bearing with retainer as shown in FIGS. 1 and 3 is subjected to an axial load, e.g. a leftward load on the outer ring 1, or a rightward load on the inner ring 2, the guide rings 11 may be displaced leftward in FIGS. 1 and 3, so that the convex rollers 3 in the right row supporting the axial load tend to be skewed.
When the convex rollers 3 supporting the load are skewed, frictional forces between the rolling face of the convex rollers 3 and the outer ring raceway 5, and between the rolling face of the convex rollers 3 and the inner ring raceway 6 become excessive, the rotation torque of the bearing becomes large. And, in the worst case, seizure etc. is undesirably caused.
Incidentally, no special problem will occur in the case when the convex rollers 3 exposed to substantially no axial load (e.g. the convex rollers 3 in the left row in FIGS. 1 and 3 in the care mentioned above) are skewed.
In the construction where the guide ring 11 is guided by the inner ring 2 as shown in FIG. 3, the inner peripheral face of the guide ring 11 comes slidably into contact with the outer peripheral face of the inner ring 2 in the direction of revolution. This is referred to as "revolution slide".
In addition, the revolution slide occurs between the guide ring 11 and the convex rollers 3.
Such revolution slide will produce frictional heat, so that the temperature within the self-aligning roller bearing is increased, which may reduce the performance of the self-aligning roller bearing.
The copending JP Patent Application No. H6-202264 laid open under No. KOKAI 8-28576 discloses a self-aligning roller bearing, which is prevented from being skewed as shown in FIGS. 4 to 6.
The self-aligning roller bearing with retainer in the copending JP patent application has retainers 4 therein which are, like the retainers 4 of the prior art construction as shown in FIGS. 1 and 2, made from a metal plate through press-forming, and comprised of a frustum shaped main portion 7 having a larger diameter end edge portion and a smaller diameter end edge portion, an outward flange portion 8 extending radially outwards from the larger diameter end edge portion, and an inward flange portion 9 extending radially inwards from the smaller end edge portion.
There are a plurality of pockets 10 formed in the main portions 7, so that the respective pockets receive rotatably a convex roller 3, respectively. Specifically, the respective pockets 10 are defined by a pair of crossbars 7a and the outward and inward flange portions 8, 9.
The main portions 7 are located radially outward of the pitch circle of the convex rollers 3, so that the convex rollers 3 are prevented from moving radially outwards out of the main portion 7 through the pockets 10.
In addition, in the case of FIGS. 4 to 6, a projection 13 is formed on either side of each of the crossbars 7a in the main portion 7, and located at the central portion of the circumferential opposite ends of the respective pockets 10.
The projections 13 protrude circumferentially and have a tip end which is tapered such that the amount of projecting from the edge of the crossbars 7a is increased as it extends radially outwards.
Since the projections 13 are engaged with the rolling faces of the convex rollers 3, respectively, the convex rollers 3 are prevented from slipping out of the pockets 10 radially outward of the retainers 4 (upward on FIG. 4).
The inward flanges 9 have a radially outer half, the axially outside face of which is formed with a flat face 14 to prevent the radially outer half of the inward flanges 9 from being projected from the end faces 1a of the outer ring 1 and from the end faces 2a of the inner ring 2. The flat face 14 extends substantially parallel to the end face la of the outer ring 1 and to the end face 2a of the inner ring 2 when the retainers 4 are installed in the self-aligning roller bearing.
The outward flanges 8 have an axially outside face which is faced to the pockets 10 and formed with a plurality of flat guide faces 15.
The guide faces 15 circumferentially adjacent to each other are connected to each other through a connecting face 16. In other words, the guide faces 15 and connecting faces 16 are circumferentially alternately positioned.
The guide faces 15 are closer and parallel to the axially inside end faces 17 of the convex rollers 3 held within the pockets 10 when installed in the self-aligning roller bearing. In this state, the convex rollers 3 are guided by the guide faces 15, so that the rotation axis of the convex rollers 3 is prevented from being tilted or skewed from the normal condition.
In addition, when a pair of retainers 4 are installed in the self-aligning roller bearing so as to support the convex rollers 3 in rows, the axially inside end faces 18 of the outward flange portion 8 of the retainers 4 are circumferentially engaged with each other.
Accordingly, the retainers 4 are rotated in the same direction guided by each other.
The operation of the self-aligning roller bearing with retainer of the copending JP patent application for supporting the rotating shaft inside the housing is substantially the same as that of the prior art self-aligning roller bearing with retainer previously explained.
Specifically, since the axially inside end faces 17 of the convex rollers 3 are guided by the guide faces 15 on the axially outside face of the outward flanges 8, the relationship between the end faces 17 and the guide faces 15 does not change regardless of the operation of the self-aligning roller bearing.
In other words, even when the outer ring 1 or inner ring 2 experiences the axial load so that the axial position relationship between the outer ring raceway 5 and inner ring raceway 6 is displaced, there is no change in the clearance between the end faces 17 of the convex rollers 3 and the guide faces 15. Consequently, even when the convex rollers 3 in one row can be axially displaced due to the axial load, the convex rollers 3 in the other row (also in the one row) are hardly skewed.
In the construction as shown in FIGS. 4 to 6, the outward flange portions 8 in the pair of retainers 4 are abutted to each other, and the guide rings 11 as in the prior art construction in FIGS. 1 to 3 are omitted. Consequently, not only the revolution slide is reduced and the frictional heat produced in the bearing is made small, but also the self-aligning roller bearing is lubricated efficiently.
When the interior of the self-aligning roller bearing is lubricated with the inner ring 2 rotated in operation, lubricant oil is supplied generally through e.g. an the inlet port 24 (see FIG. 9) in the axially central portion of the outer ring 1 to the portion where the convex rollers 3 are provided.
In the prior art constructions in FIGS. 1 to 3, the guide ring 11 are reluctant to the flow of lubricant oil. On the other hand, in the roller bearing of the copending JP patent application as in FIGS. 4 to 6 the flow of lubricant oil is smooth and the production cost is lower because the guide ring 11 of the prior art constructions does not exist and the number of parts is reduced.
Although the skew prevention of the convex rollers 3 is improved in the self-aligning roller bearing of the copending JP patent application in FIGS. 4 to 6 comparing with the prior art constructions as shown in FIGS. 1 to 3, the improvement in the following points are still desired.
Specifically, in order to more securely prevent the convex rollers 3 from being skewed, the end faces 17 of the convex rollers 3 must be guided by the guide faces 15 of the outward flange portions 8 while the displacement of the convex rollers 3 must be prevented in the pockets 10.
Specifically, the length of the pockets 10, that is the axial inner dimension of the retainers 4 is made closer to the axial size of the convex rollers 3, so that the convex rollers 3 are hardly displaced or inclined with reference to the pockets 10.
Since the center of the retainer 4 having a larger diameter is not inclined with reference to the center of the self-aligning roller bearing, or even inclined, its inclination angle is very small.
Accordingly, if the convex rollers 3 are prevented from being displaced with reference to the pockets 10, the convex rollers 3 are effectively prevented from being skewed.
However, it is generally difficult to precisely specify, with reference to the dimensions of the convex roller 3, the dimensions of the pocket 10 formed by punching the metal plate, and those of the outwardly flanged portion 8 formed by bending the metal plate. More specifically, since it is necessary to adequately maintain the accuracy of the flatness and evenness of the guide faces 15 faced to the respective pockets 10, over the whole surface, the die required is complicated and difficult to manufacture. Therefore even though possible, the manufacturing costs of the retainer 4 are increased. Moreover, since the length of rubbing engagement between the axially inside end face 17 of the convex roller 3 and the axially outside side face of the outwardly flanged portion 8 is long, the frictional force acting at the rubbing portion is increased. Hence the torque required to rotate the convex roller 3, and the rotation torque for the self aligning roller bearing with retainer is increased. Furthermore, since the width of the gap formed between the guide face 15 of the outwardly flanged portion 8 and the end face 17 of the convex roller 3 is very small, the flow of lubricating oil through the gap is limited. Hence it is difficult to maintain adequate lubrication of the self aligning roller bearing with retain.